US7852813B2 - System and method for acquiring cell in a frequency overlay communication system - Google Patents
System and method for acquiring cell in a frequency overlay communication system Download PDFInfo
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- US7852813B2 US7852813B2 US11/510,000 US51000006A US7852813B2 US 7852813 B2 US7852813 B2 US 7852813B2 US 51000006 A US51000006 A US 51000006A US 7852813 B2 US7852813 B2 US 7852813B2
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W48/00—Access restriction; Network selection; Access point selection
- H04W48/08—Access restriction or access information delivery, e.g. discovery data delivery
- H04W48/12—Access restriction or access information delivery, e.g. discovery data delivery using downlink control channel
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/309—Measuring or estimating channel quality parameters
- H04B17/318—Received signal strength
- H04B17/327—Received signal code power [RSCP]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/382—Monitoring; Testing of propagation channels for resource allocation, admission control or handover
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
Definitions
- the present invention relates generally to a system and method for performing cell acquisition in a communication system, and in particular, to a method and system for acquiring cells in a communication system using a frequency overlay scheme (“frequency overlay communication system”).
- frequency overlay communication system a frequency overlay scheme
- broadband communication systems With the development of communication systems, the types of necessary services provided in communication systems are diversified, raising the need for a broadband communication system supporting broadband service. However, due to limited frequency resources in communication systems, broadband communication systems also have limitations on available frequency bands. In addition, because backward compatibility with the previously deployed communication systems should also be taken into consideration, design of broadband communication systems is difficult.
- a broadband communication system that is overlaid with an existing communication system in a particular frequency band is a typical scheme.
- a mobile station (MS) existing in the broadband communication system is overlaid in the particular frequency band, and an MS of the existing communication system should be able to perform cell acquisition for recognizing a base station (BS) from which they can receive services.
- BS base station
- the BS and the MS should acquire mutual synchronization for signal transmission/reception, and for the synchronization acquisition, the BS transmits a synchronization signal so that the MS becomes aware of the start of the frame transmitted by the BS. Then the MS receives the synchronization signal transmitted by the BS, detects frame timing of the BS from the synchronization signal, and demodulates the frame. Generally, a particular preamble sequence predefined by the BS and the MS is used as the synchronization signal.
- a preamble sequence used in an Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA) communication system should have a low Peak-to-Average Power Ratio (PAPR), and the preamble sequence is used for acquiring coarse synchronization and fine synchronization.
- OFDM Orthogonal Frequency Division Multiplexing
- OFDMA Orthogonal Frequency Division Multiple Access
- the transmission signal transmitted by the BS is distorted while passing through a wireless channel, and the MS receives the distorted transmission signal.
- the MS acquires time/frequency synchronization for the received distorted transmission signal using a predefined preamble sequence, performs channel estimation on the synchronization-acquired signal, and demodulates the channel-estimated signal into frequency-domain symbols through Fast Fourier Transform (FFT). After demodulating the frequency-domain symbols, the MS (or receiver) decodes the demodulated symbols into information data using a decoding scheme corresponding to the coding scheme used in the BS.
- FFT Fast Fourier Transform
- the preamble sequence is used for frame timing synchronization, frequency synchronization, and channel estimation.
- Each BS uses its own unique frame sequence. Therefore, the MS has information on every preamble sequence, detects the preamble sequence having the maximum correlation value through correlation calculation between a preamble sequence included in a received frame and every preamble sequence, and recognizes the BS corresponding to the detected preamble sequence as a serving BS that is providing the service to the MS.
- the preamble sequence should be designed such that it can distinguish a BS of the existing communication system from a BS of the broadband communication system. That is, the preamble sequence used in the existing communication system should be designed such that it can be used even in the broadband communication system. In addition, the preamble sequence of the broadband communication system should be designed such that its correlation with the preamble sequence of the existing communication system is minimized.
- the MS whose operation mode is set to enable communication with the existing communication system, should be able to perform cell acquisition when it is located in the broadband communication system.
- the MS whose operation mode is also set to enable communication with the broadband communication system, should also be able to perform cell acquisition when it is located in the existing communication system.
- an object of the present invention to provide a system and method for generating a reference signal for cell acquisition in a frequency overlay communication system.
- a system for performing cell acquisition in a frequency overlay communication system having a first frequency band and a second frequency band including the first frequency band.
- the system includes a base station (BS) for generating a reference signal used for identifying a cell using a specific sequence in a predetermined frequency band, and transmitting the reference signal; and a mobile station (MS) for receiving the reference signal to determine whether the BS uses the first frequency band or the second frequency band, determining a reference signal having a maximum correlation value through correlation calculation with at least one predefined sequence, and detecting a BS identifier (ID) corresponding to the determined reference signal.
- BS base station
- MS mobile station
- a method for performing cell acquisition by a mobile station (MS) in a frequency overlay communication system having a first frequency band and a second frequency band including the first frequency band includes receiving a reference signal used for identifying a cell using a specific sequence in a predetermined frequency band; determining whether a corresponding base station (BS) uses the first frequency band or the second frequency band; determining a reference signal having the maximum correlation value through correlation calculation with at least one predefined sequence; and detecting a BS identifier (ID) corresponding to the determined reference signal.
- BS base station
- a method for transmitting a reference signal for cell acquisition by a base station (BS) in a frequency overlay communication system having a first frequency band and a second frequency band including the first frequency band includes generating a reference signal for cell identification using a specific sequence in a predetermined frequency band; multiplexing the reference signal with data and a control signal; and performing Inverse Fast Fourier Transform (IFFT) on the multiplexed signal and transmitting the IFFT-processed signal.
- IFFT Inverse Fast Fourier Transform
- FIG. 1 is a diagram illustrating a frequency allocation operation in a frequency overlay communication system according to the present invention
- FIG. 2 is a diagram illustrating a transceiver module used in a frequency overlay communication system according to the present invention
- FIG. 3 is a diagram illustrating an alternative transceiver module used in a frequency overlay communication system according to the present invention
- FIG. 4 is a diagram illustrating a downlink frame structure of a frequency overlay communication system according to the present invention.
- FIG. 5 is a diagram illustrating a structure of an EB-BS transmission apparatus in a frequency overlay communication system according to the present invention
- FIG. 6 is a diagram illustrating a structure of an EB-BS reception apparatus in a frequency overlay communication system according to the present invention
- FIG. 7 is a diagram illustrating a structure of an EB-MS transmission apparatus in a frequency overlay communication system according to the present invention.
- FIG. 8 is a diagram illustrating a structure of an EB-MS reception apparatus in a frequency overlay communication system according to the present invention.
- FIG. 9 is a diagram illustrating a structure of an NB-MS transmission apparatus in a frequency overlay communication system according to the present invention.
- FIG. 10 is a diagram illustrating a structure of an NB-MS reception apparatus in a frequency overlay communication system according to the present invention.
- FIG. 11 is a diagram illustrating a detailed structure of a PCH generator in a frequency overlay communication system according to the present invention.
- FIG. 12 is a diagram illustrating a PCH generation process according to the present invention.
- FIG. 13 is a flowchart illustrating a process in which an EB-MS performs cell acquisition, synchronization, and channel estimation in a frequency overlay communication system according to the present invention
- FIG. 14 is a flowchart illustrating a process in which an NB-MS performs cell acquisition, synchronization, and channel estimation in a frequency overlay communication system according to the present invention.
- FIG. 15 is a flowchart illustrating a process in which an NB-MS or an EB-MS performs cell acquisition according to the present invention.
- the present invention provides a system and method in which a base station (BS) generates a reference signal for cell acquisition, and a mobile station (MS) performs cell acquisition using the reference signal in a communication system using a frequency overlay scheme (“frequency overlay communication system”).
- the reference signal includes a preamble sequence and a pilot signal.
- the preamble sequence can be generated by concatenating Golay Complementary Sequences (GCS).
- an MS using a non-overlaid frequency band is referred to as a Narrow Band-Mobile Station (NB-MS), and an MS using an extended frequency band including the non-overlaid frequency band is referred to as an Extended Band-Mobile Station (EB-MS).
- NB-MS Narrow Band-Mobile Station
- EB-BS Extended Band-Base Station
- NB-BS Narrow Band-Base Station
- EB-BS Extended Band-Base Station
- either one of the NB-BS and the EB-BS may exist, or the NB-BS and the EB-BS may both coexist. Therefore, when the NB-BS and the EB-BS coexist in the frequency overlay communication system, backward compatibility between the NB-BS and the EB-BS is very important.
- FIG. 1 shows a frequency allocation operation in a frequency overlay communication system according to the present invention.
- the existing communication system is a narrow band (NB) communication system having a center frequency f c1 (“NB communication system”).
- NB communication system may require extension of the frequency bandwidth due to diversification of the services and an increase in the required transmission capacity. Therefore, a communication system with extended frequency bandwidth can be considered, and the communication system with the extended frequency band (“EB communication system”) can be designed such that it is overlaid with the NB communication system in the frequency band. In this case, in FIG.
- the EB communication system has a center frequency f c2
- terms such as the “Narrow Band” and “Extended Band” are used for convenience in that the NB communication system can be relatively narrower in frequency bandwidth than the EB communication system, this does not imply that the frequency band used in the NB communication system should be absolutely narrow.
- the reasons for extending the frequency bandwidth using the frequency overlay scheme are as follows.
- the use of the frequency overlay scheme increases frequency resource efficiency in the overlaid frequency band.
- the frequency resource efficiency is very important for service providers because service providers can benefit from their subscribers in proportion to the frequency resource efficiency.
- FIG. 2 shows a transceiver module used in a frequency overlay communication system according to the present invention.
- IFFT Inverse Fast Fourier Transform
- FFT Fast Fourier Transform
- a BS 200 can support services to an MS 1 240 of the NB communication system and an MS 2 260 of the EB communication system with an M-point IFFT/FFT module without separately including an N-point IFFT/FFT module.
- M-point IFFT/FFT module In order to support services to the MSs of both the NB communication system and the EB communication system with one IFFT/FFT module, i.e., the M-point IFFT/FFT module, in this way, it is necessary to provide a guard band between boundary frequency bands of the NB communication system and the EB communication system. A specific size of the guard band depends upon performance of a band-pass filter (BPF).
- BPF band-pass filter
- FIG. 3 shows an alternative transceiver module used in a frequency overlay communication system according to the present invention.
- the system when the system is extended, it is preferable to deploy BSs using the frequency overlay scheme.
- the BSs using the frequency overlay scheme cannot be deployed in a particular region, and the BSs using the N-point IFFT/FFT module used in the exiting NB communication system are maintained.
- the BS of FIG. 3 if it is an NB-BS, should take into account even the IFFT/FFT points of the transceiver module used in the EB communication system.
- An NB-BS 300 uses only an N-point IFFT/FFT module. If there is only the guard band between the frequency band used in the EB communication system and the frequency band used in the NB communication system, the NB-BS 300 can communicate not only with an MS 1 340 having an N-point IFFT/FFT module but also with an MS 2 360 having an M-point IFFT/FFT module, using only the N-point IFFT/FFT module.
- a specific size of the guard band depends upon performance of a BPF, and the guard band is not related to the present invention, so a detailed description will be omitted.
- the signal actually desired by a receiver is mapped only to the N-point part in the (2 m ⁇ N)-point IFFT module.
- the data after passing through the M-point IFFT module is up-converted to a band of a carrier frequency f c1 used in the NB communication system through a band-pass filtering process.
- the up-converted data is subject to band-pass filtering taking into account a bandwidth W EB occupied by the (2 m ⁇ N) points.
- the band-pass filtered data is transmitted via a transmission antenna.
- an NB-MS corresponding to a receiver receives the signal transmitted from the transmitter, i.e. BS 300 , via a reception antenna. Thereafter, the MS performs band-pass filtering on the received signal according to a bandwidth W NB for the N points.
- the band-pass filtered signal can be restored to its original signal through an N-point FFT module 340 . That is, the NB-MS finds a position of the resources allocated thereto according to a control signal, and then restores the traffic signal.
- FIG. 4 shows a downlink frame structure of a frequency overlay communication system according to the present invention.
- a downlink frame 470 of the EB communication system (hereinafter referred to as an “EB communication system's downlink frame”) includes a downlink frame 400 currently used in the NB communication system (hereinafter referred to as an “NB communication system's downlink frame”), a downlink frame dependently added to the NB communication system for the EB communication system, i.e. NB communication system-dependent downlink frame 450 , and a guard band 430 between the NB communication system's downlink frame 400 and the NB communication system-dependent downlink frame 450 .
- NB communication system's downlink frame a downlink frame dependently added to the NB communication system for the EB communication system
- guard band 430 between the NB communication system's downlink frame 400 and the NB communication system-dependent downlink frame 450 .
- the NB communication system's downlink frame 400 includes a Narrow Band-Preamble Channel (NB-PCH), a Narrow Band-Pilot Channel (NB-PICH), a Narrow Band-Traffic Channel (NB-TCH), and a Narrow Band-Control Channel (NB-CCH).
- NB-PCH Narrow Band-Preamble Channel
- NB-PICH Narrow Band-Pilot Channel
- NB-TCH Narrow Band-Traffic Channel
- NB-CCH Narrow Band-Control Channel
- the NB communication system-dependent downlink frame 450 includes a Narrow Band-Dependent Preamble Channel (NB-DPCH), a Narrow Band-Dependent Pilot Channel (NB-DPICH), a Narrow Band-Dependent Traffic Channel (NB-DTCH), and a Narrow Band-Dependent Control Channel (NB-DCCH).
- NB-DPCH Narrow Band-Dependent Preamble Channel
- NB-DPICH Narrow Band-Dependent Pilot Channel
- NB-DTCH Narrow Band-Dependent Traffic Channel
- NB-DCCH Narrow Band-Dependent Control Channel
- the EB communication system's downlink frame 470 includes the NB communication system's downlink frame 400 , the guard band 430 , and the NB communication system-dependent downlink frame 450 .
- the EB communication system's downlink channel structure is as follows.
- An Extended Band-Preamble Channel (EB-PCH) of the EB communication system includes the NB-PCH and the NB-DPCH.
- An Extended Band-Pilot Channel (EB-PICH) of the EB communication system includes the NB-PICH and the NB-DPICH.
- An Extended Band-Traffic Channel (EB-TCH) of the EB communication system includes the NB-TCH and the NB-DTCH.
- an Extended Band-Control Channel (EB-CCH) of the EB communication system includes the NB-CCH and the NB-DCCH.
- the EB-PCH should not only include the intact NB-PCH, but also should be designed to minimize its correlation with the NB-PCH and maximize time/frequency synchronization and channel estimation performances. Therefore, the NB-DPCH should necessarily have a structure dependent on the NB-PCH. In addition, the EB-PCH should be designed so that it is available not only for the time/frequency synchronization and channel estimation, but also for cell acquisition.
- the EB-PICH includes not only the intact NB-PICH, but also includes the NB-DPICH having a structure dependent on the NB-PICH.
- the use of the EB-PICH cannot only achieve cell acquisition as described above, but also performs time/frequency synchronization and channel estimation, similar to the EB-PCH.
- an EB-BS transmission apparatus in a frequency overlay communication system includes scheduler 511 , PCH generator 513 , PICH generator 515 , a DL-TCH generator 517 , a DL-CCH generator 519 , multiplexer (MUX) 521 , M-point IFFT unit 523 , and Radio Frequency (RF) transmitter 525 .
- scheduler 511 User data for all MSs serviced in the EB communication system is delivered to scheduler 511 , and scheduler 511 schedules the user data according to a predetermined scheduling scheme, and outputs the scheduled user data to DL-TCH generator 517 and resource allocation information for the scheduled user data to DL-CCH generator 519 and multiplexer 521 .
- the scheduling operation of scheduler 511 is not directly related to the present invention, so a detailed description will be omitted.
- PCH generator 513 generates a PCH, i.e. an EB-PCH including an NB-PCH, a guard band signal and an NB-DPCH, and outputs the PCH to multiplexer 521 .
- PICH generator 515 generates a PICH, i.e. an EB-PICH including an NB-PICH, a guard band signal and an NB-DPICH, and outputs the PICH to multiplexer 521 .
- DL-TCH generator 517 generates a DL-TCH, i.e. an EB-TCH including an NB-TCH and an NB-DTCH, and outputs the DL-TCH to multiplexer 521 .
- DL-CCH generator 519 generates a DL-CCH, i.e. an EB-CCH including an NB-CCH and an NB-DCCH, and outputs the DL-CCH to multiplexer 521 .
- Multiplexer 521 generates a downlink channel by multiplexing the PCH output from PCH generator 513 , the PICH output from PICH generator 515 , the DL-TCH output from DL-TCH generator 517 , and the DL-CCH output from DL-CCH generator 519 in a time domain and a frequency domain according to the resource allocation information output from scheduler 511 , and outputs the downlink channel to M-point IFFT unit 523 .
- M-point IFFT unit 523 performs M-point IFFT on the downlink channel signal output from multiplexer 521 , and outputs the IFFT-processed signal to RF transmitter 525 .
- RF transmitter 525 performs a transmission process, i.e. RF process, on the signal output from M-point IFFT unit 523 , and transmits the RF-processed signal over the air via an antenna.
- the EB-BS transmission apparatus in the frequency overlay communication system according to the present invention has been described so far with reference to FIG. 5 .
- FIG. 6 a description will be made of an EB-BS reception apparatus in a frequency overlay communication system according to the present invention.
- FIG. 6 is a diagram illustrating a structure of an EB-BS reception apparatus in a frequency overlay communication system according to the present invention.
- the EB-BS reception apparatus includes RF receiver 611 , M-point FFT unit 613 , and demultiplexer (DEMUX) 615 .
- DEMUX demultiplexer
- RF receiver 611 performs a reception process on an RF signal received via an antenna, i.e. converts the RF signal into a baseband signal, and outputs the baseband signal to M-point FFT unit 613 .
- M-point FFT unit 613 performs M-point FFT on the baseband signal output from RF receiver 611 , and outputs the FFT-processed signal to demultiplexer 615 .
- Demultiplexer 615 demultiplexes the signal output from M-point FFT unit 613 in the time domain and the frequency domain, and outputs a Synchronization Channel (SCH), a Random Access Channel (RACH), an Uplink-Traffic Channel (UL-TCH) and an Uplink-Control Channel (UL-CCH).
- SCH Synchronization Channel
- RACH Random Access Channel
- UL-TCH Uplink-Traffic Channel
- UL-CCH Uplink-Control Channel
- the SCH is an Extended Band-Synchronization Channel (EB-SCH) including a Narrow Band-Synchronization Channel (NB-SCH) and a Narrow Band-Dependent Synchronization Channel (NB-DSCH).
- the RACH is an Extended Band-Random Access Channel (EB-RACH) including a Narrow Band-Random Access Channel (NB-RACH) and a Narrow Band-Dependent Random Access Channel (NB-DRACH).
- FIG. 7 shows an EB-MS transmission apparatus in a frequency overlay communication system according to the present invention.
- the EB-MS transmission apparatus includes SCH generator 711 , RACH generator 713 , UL-TCH generator 715 , UL-CCH generator 717 , multiplexer 719 , M-point IFFT unit 721 , and RF transmitter 723 .
- the RACH generator 713 generates an RACH, i.e. an EB-RACH including an NB-RACH and an NB-DRACH, and outputs the RACH to multiplexer 719 .
- UL-TCH generator 715 generates a UL-TCH, i.e. an EB-TCH including an NB-TCH and an NB-DTCH, and outputs the UL-TCH to multiplexer 719 .
- the UL-CCH generator 717 generates a UL-CCH, i.e. an EB-CCH including an NB-CCH and an NB-DCCH, and outputs the UL-CCH to multiplexer 719 .
- SCH generator 711 , RACH generator 713 , UL-TCH generator 715 and UL-CCH generator 717 generate all channels available in the EB communication system by way of example in order to support the EB communication system, they can also generate the corresponding channels under the control of the EB communication system.
- RACH generator 713 generates only the NB-RACH when the EB-BS permits the EB-MS to perform random access through the NB-RACH.
- FIG. 8 shows an EB-MS reception apparatus in a frequency overlay communication system according to the present invention.
- the EB-MS reception apparatus includes RF receiver 801 , demultiplexer 803 for performing demultiplexing in the time domain, cell acquisitor 805 , M-point FFT unit 807 , and demultiplexer 809 for performing demultiplexing in the frequency domain.
- RF receiver 801 performs a reception process on an RF signal received via an antenna, i.e. converts the RF signal into a baseband signal, and outputs the baseband signal to demultiplexer 803 .
- Demultiplexer 803 demultiplexes its input signal in the time domain and separates a preamble channel, i.e. PCH, from the input signal.
- the PCH is input to cell acquisitor 805 and M-point FFT unit 807 , and cell acquisitor 805 acquires a BS, i.e. cell, from which the EB-MS can receive service, through correlation calculation on a preamble sequence included in the PCH.
- the EB-MS reception apparatus receives all channels available in the EB communication system by way of example in order to support the EB communication system, it can also selectively receive the corresponding channels under the control of the EB communication system.
- the EB-MS reception apparatus can receive only either one of or both of the NB-TCH and the NB-DTCH under the control of the EB-BS.
- FIG. 9 shows an NB-MS transmission apparatus in a frequency overlay communication system according to the present invention.
- the NB-MS transmission apparatus is similar to the EB-MS transmission apparatus of FIG. 7 . However, the frequency bandwidth and center frequency of the NB-MS transmission apparatus is different from the EB-MS transmission apparatus. Therefore, it should be noted that the number of points of an N-point IFFT unit 921 in the NB-MS transmission apparatus is less than the number of points of the M-point IFFT unit in the EB-MS.
- FIG. 10 shows an NB-MS reception apparatus in a frequency overlay communication system according to the present invention.
- the NB-MS reception apparatus is similar to the EB-MS reception apparatus of FIG. 8 . However, the frequency bandwidth and center frequency of the NB-MS reception apparatus is different from the EB-MS reception apparatus.
- the number of points of an N-point FFT unit 1007 in the NB-MS reception apparatus is less than the number of points of the M-point FFT unit in the EB-MS.
- the NB-MS can be located either in the coverage area of the EB-BS, or in the coverage area of the NB-BS.
- the NB-MS can perform cell acquisition according to the present invention regardless of whether it is located in the coverage area of the EB-BS or located in the coverage area of the NB-BS.
- the NB-MS or the EB-MS uses two kinds of information: one is an NB-PCH which is preamble information for the NB band, and another is an NB-DPCH which is preamble information for bands other than the NB band.
- the NB-MS or the EB-MS acquires the NB-PCH and the NB-DPCH while shifting the center frequency at different intervals.
- a cell acquisition process performed by the NB-MS or the EB-MS is described below with reference to the FIG. 15 .
- FIG. 11 shows a PCH generator in a frequency overlay communication system according to the present invention.
- preamble sequence according to the present invention is generated using Golay complementary sequences.
- Golay complementary sequences can be expressed as
- the Golay complementary sequences are mapped to IFFT inputs according to a predetermined mapping scheme, an IFFT output has a Peak-to-Average Power Ratio (PAPR) below 3 dB. Therefore, the Golay complementary sequences are useful for generation of a preamble sequence requiring a low PAPR.
- the Golay complementary sequences can be usefully applied even to the frequency overlay communication system according to the present invention. This is because according to the characteristics of the Golay complementary sequences, a sequence obtained by concatenating the Golay complementary sequences C A (u) and C B (u) is also a Golay complementary sequence.
- the sequence generated by concatenating a Golay complementary sequence used in the NB-BS using the center frequency f c1 and the frequency bandwidth 10 MHz, to a Golay complementary sequence used in the NB-BS using the center frequency f c2 and the frequency bandwidth 10 MHz can be used as a preamble sequence of the EB-BS using the center frequency f c3 and the frequency bandwidth 20 MHz.
- the PCH generator includes Golay Complementary Sequences (GCS) pair generator 1101 and concatenator 1103 .
- GCS Golay Complementary Sequences
- GCS pair generator 1101 generates a first Golay complementary sequence pair by selecting one Golay complementary sequence pair unused in other BSs among a plurality of Golay complementary sequence pairs according to an input BS identifier (ID). In addition, GCS pair generator 1101 generates a second Golay complementary sequence pair associated with the first Golay complementary sequence pair.
- the generated Golay complementary sequence pairs are input to concatenator 1103 , and concatenator 1103 concatenates the input Golay complementary sequence pairs to each other, and outputs a new Golay complementary sequence.
- Each of the components constituting the output Golay complementary sequence is mapped to a predetermined number of subcarriers, generating a specific PCH.
- FIG. 12 shows a PCH generation process according to the present invention.
- a GCS a 10 ( 1201 ) has A 10 1205 as a GCS pair.
- the a 10 1201 and the A 10 1205 are complementary to each other.
- a sequence generated by concatenating the GCS pair a 10 1203 and A 10 1205 to each other is a new GCS b 20 ( 1207 ).
- the GCS b 20 ( 1207 ) has B 20 1211 as a GCS pair. Therefore, a sequence generated by concatenating the GCS pair b 20 1209 and B 20 1211 to each other is a new GCS c 40 .
- the GCS c 40 is generated by concatenating B 20 1211 obtained by inverting a sign of the A 10 1205 constituting the GCS b 20 ( 1207 ), to the b 20 1209 .
- the b 20 1209 can be used for the NB-PCH
- the B 20 1211 can be used for the NB-DPCH.
- FIGS. 13 to 15 Operations performed by the EB-MS and the NB-MS using the PCH are shown in FIGS. 13 to 15 .
- FIG. 13 shows a process in which an EB-MS performs cell acquisition, synchronization, and channel estimation in a frequency overlay communication system according to the present invention.
- the EB-MS receives a PCH of a downlink frame from a particular BS, and detects a preamble sequence from the PCH.
- the EB-MS performs coarse synchronization using the detected preamble sequence, and then proceeds to step 1303 .
- the EB-MS can perform coarse synchronization, i.e. can estimate a timing offset and a frequency offset, even though it is unaware of a correct value of the preamble sequence.
- the EB-MS identifies a BS type indicating whether the BS where it is currently located is an EB-BS or an NB-BS.
- step 1305 the EB-MS detects a BS ID corresponding to a preamble sequence having the maximum correlation value through correlation calculation on the detected preamble sequence.
- step 1307 the EB-MS performs fine synchronization.
- step 1309 the EB-MS performs channel estimation using the PCH or the PICH.
- FIG. 14 shows a process in which an NB-MS performs cell acquisition, synchronization, and channel estimation in a frequency overlay communication system according to the present invention.
- the NB-MS performs a similar operation to the operation performed by the EB-MS of FIG. 13 . However, compared with the EB-MS that performs synchronization, cell acquisition and channel estimation using the EB-PCH, the NB-MS performs synchronization, cell acquisition and channel estimation using the NB-PCH and/or the NB-DPCH.
- the NB-MS receives the NB-PCH and the NB-DPCH with a time difference, and should shift the center frequency for reception of the two channels.
- FIG. 15 shows a process in which an NB-MS or an EB-MS performs cell acquisition according to the present invention.
- the NB-MS or EB-MS measures signal strengths, i.e. power values, of an NB-PCH# 2 and an NB-PCH# 2 upon its power-on.
- the power value of the NB-PCH# 1 is defined as a P_NB-PCH# 1
- the power value of the NB-PCH# 2 is defined as a P_NB-PCH# 2 .
- the NB-MS or EB-MS determines whether the P_NB-PCH# 1 and the P_NB-PCH# 2 exceed a first power threshold P_Th 1 .
- step 1503 If it is determined in step 1503 that the P_NB-PCH# 1 and the P_NB-PCH# 2 exceed the P_Th 1 , the NB-MS or EB-MS proceeds to step 1505 . However, if the P_NB-PCH# 1 and the P_NB-PCH# 2 are lower than the P_Th 1 , the NB-MS or EB-MS proceeds to step 1519 . When the P_NB-PCH# 1 and the P_NB-PCH# 2 exceed the P_Th 1 , there is a high probability that the NB-MS or EB-MS will be located in the coverage of an EB-BS.
- the NB-MS or EB-MS determines whether an absolute value of the value determined by subtracting the P_NB-PCH# 2 from the P_NB-PCH# 1 is less than a second threshold P_Th 2 in order to correctly recognize whether its current BS is an EB-BS or an NB-BS. This is based on the assumption that the P_NB-PCH# 1 and the P_NB-PCH# 2 are ideally equal to each other because the EB-BS manages an EB-PCH, i.e. a preamble channel composed of the NB-PCH# 1 and the NB-PCH# 2 .
- the NB-MS or EB-MS proceeds to step 1507 when an absolute value of the value determined by subtracting the P_NB-PCH# 2 from the P_NB-PCH# 1 is less than the P_Th 2 . If the P_Th 2 is less than or equal to the absolute value of the value determined by subtracting the P_NB-PCH# 2 from the P_NB-PCH# 1 , the NB-MS or EB-MS proceeds to step 1513 .
- step 1507 the NB-MS or EB-MS determines whether the P_NB-PCH# 1 from the P_NB-PCH# 2 are complementary to each other. If they are complementary to each other, the NB-MS or EB-MS proceeds to step 1509 . If they are not complementary to each other, the NB-MS or EB-MS proceeds to step 1513 .
- step 1509 the NB-MS or EB-MS recognizes that its current BS is an EB-BS.
- step 1511 the NB-MS or EB-MS performs cell acquisition using a PCH, i.e. an EB-PCH composed of the NB-PCH# 1 and the NB-PCH# 2 .
- step 1513 the NB-MS or EB-MS determines whether the P_NB-PCH# 1 exceeds the P_NB-PCH# 2 . If it is determined in step 1513 that the P_NB-PCH# 1 exceeds the P_NB-PCH# 2 , the NB-MS or EB-MS proceeds to step 1515 . If the P_NB-PCH# 1 is less than the P_NB-PCH# 2 , the NB-MS or EB-MS proceeds to step 1523 .
- step 1515 the NB-MS or EB-MS recognizes that its current BS is a BS (NB 1 ) using the NB-PCH# 1 , because the P_NB-PCH# 1 is greater than the P_NB-PCH# 2 .
- step 1517 the NB-MS or EB-MS performs cell acquisition using the NB-PCH# 1 .
- step 1519 the NB-MS or EB-MS determines whether the P_NB-PCH# 1 exceeds the P_Th 1 . If it is determined that the P_NB-PCH# 1 exceeds the P_Th 1 , the NB-MS or EB-MS proceeds to step 1515 . If the P_NB-PCH# 1 is less than the P_Th 1 , the NB-MS or EB-MS proceeds to step 1521 . In step 1521 , the NB-MS or EB-MS determines whether the P_NB-PCH# 2 exceeds the P_Th 1 .
- step 1521 If it is determined in step 1521 that the P_NB-PCH# 2 exceeds the P_Th 1 , the NB-MS or EB-MS proceeds to step 1523 . If the P_NB-PCH# 2 is less than the P_Th 1 , the NB-MS or EB-MS proceeds to step 1501 .
- step 1523 the NB-MS or EB-MS recognizes that its current BS is a BS (NB 2 ) using the NB-PCH# 2 , because the P_NB-PCH# 2 is greater than the P_NB-PCH# 1 .
- step 1525 the NB-MS or EB-MS performs cell acquisition using the NB-PCH# 2 .
- the present invention allows an MS to perform cell acquisition in a frequency overlay communication system, facilitating efficient communication.
Abstract
Description
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KR1020050078356A KR100800658B1 (en) | 2005-08-25 | 2005-08-25 | System and method for acuiring cell in a frequency overlay communication system |
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US20070054681A1 (en) | 2007-03-08 |
KR20070023965A (en) | 2007-03-02 |
KR100800658B1 (en) | 2008-02-01 |
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